plugin-barman-cloud fails with Istio sidecar injection enabled

### **Description**
When using CloudNativePG with the plugin-barman-cloud.cloudnative-pg.io plugin in a namespace where Istio sidecar injection is enabled, the operator fails to create Pods.

### **Environment**
CNPG version: 1.26.1
Kubernetes version: v1.29.14
Istio version: 1.18.2

### **Steps to reproduce**
1. Create a namespace with Istio injection enabled
2. Deploy CNPG Cluster with plugin-barman-cloud enabled
3. Observe the operator logs and Pod creation

### **Actual result**
Pods cannot be created. Operator logs show:
```
{"level":"info","ts":"2025-09-11T11:10:20.313679675Z","msg":"Creating new Pod to reattach a PVC","controller":"cluster","controllerGroup":"postgresql.cnpg.io","controllerKind":"Cluster","Cluster":{"name":"pg-cluster-test2","namespace":"test2"},"namespace":"test2","name":"pg-cluster-test2","reconcileID":"6bb22819-9916-4040-b8b6-e5e408e0db7a","pod":"pg-cluster-test2-1","pvc":"pg-cluster-test2-1"}
{"level":"error","ts":"2025-09-11T11:10:20.381608713Z","msg":"Reconciler error","controller":"cluster","controllerGroup":"postgresql.cnpg.io","controllerKind":"Cluster","Cluster":{"name":"pg-cluster-test2","namespace":"test2"},"namespace":"test2","name":"pg-cluster-test2","reconcileID":"6bb22819-9916-4040-b8b6-e5e408e0db7a","error":"unable to create Pod: Pod \"pg-cluster-test2-1\" is invalid: spec.initContainers[2].startupProbe: Forbidden: may not be set for init containers without restartPolicy=Always","stacktrace":"sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).reconcileHandler\n\tpkg/mod/sigs.k8s.io/controller-runtime@v0.21.0/pkg/internal/controller/controller.go:353\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).processNextWorkItem\n\tpkg/mod/sigs.k8s.io/controller-runtime@v0.21.0/pkg/internal/controller/controller.go:300\nsigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).Start.func2.1\n\tpkg/mod/sigs.k8s.io/controller-runtime@v0.21.0/pkg/internal/controller/controller.go:202"}
```

### **Expected result**
Pods should be created successfully,
WAL archiver / backup plugin should work correctly,
Istio injection should either be compatible or possible to disable only for backup/archiver Pods.

Commencez par les étapes de reproduction indiquées en utilisant CloudNativePG 1.26.1, Kubernetes 1.29.14, Istio 1.18.2 et le plugin-barman-cloud plugin. Examinez le chemin de création des Pods de l’opérateur ainsi que l’erreur de validation initContainer startupProbe signalée au démarrage. Le travail est considéré comme terminé lorsque le Cluster crée correctement des Pods avec l’injection Istio activée et que l’archivage WAL ou la sauvegarde fonctionne comme prévu.

Rédigé par le modèle d'indexation à partir du texte de l'issue.